Dialkylcyclohexylamines are useful intermediates for the manufacture of economically important herbicides, fungicides, plant-growth regulants and other biologically active chemicals. Particularly useful as regards selectivity in action are the 2,6-dialkylcyclohexylamines where the alkyl moieties may be methyl or ethyl; both the same or either alkyl.
Typically such compounds, and more specifically 2,6-dimethylcyclohexylamine and 2-ethyl-6-methylcyclohexylamine, were previously prepared by the hydrogenation of the corresponding aniline or nitrobenzene, or by amination of the cyclohexanol or cyclohexanone. However, the 2,6-dialkyl derivatives of such compounds are not readily available. 2,6-Dimethylphenol is available in commercial quantities.
In the past, several methods have been devised for the conversion of phenols including alkylphenols to the corresponding anilines. The best of these are the catalytic methods, such as described in U.S. Pat. No. 3,931,298 describing the conversion of 2,6-dimethylphenol (2,6-DMP) to 2,6-dimethylaniline (2,6-DMA) in the presence of hydrogen, and ammonia over a hydrogen-transfer catalyst, preferably palladium, and a cyclohexanol as co-catalyst. As set forth therein the 2,6-DMP is converted to 2,6-DMA in yields of about 65 to 78%. The 2,6-dimethylcyclohexylamine (2,6-DMCHA) is reported in only trace amounts among the products.
U.S. Pat. No. 3,272,865 describes the direct amination by ammonia of certain specific phenols over Group 5B, 6 and 7B catalysts to the corresponding aniline. Dimethylphenols and dimethylanilines are not mentioned therein nor is there mention of the synthesis of presence of any cyclohexylamine among the products.